This invention relates to binding assays for use in diagnostic analysis of liquid specimens and, more particularly, to a diagnostic system capable of detecting the presence of IgE class antibodies for allergy screening.
One characteristic of mammals and other highly developed animals is the ability to protect themselves against the veritable onslaught of invading organisms and foreign material encountered on a constant or periodic basis. The protection originates in the initiation by the organism or foreign material of an immunogenic response in the animal. An important aspect of this immunogenic response is the production of immunoglobulins, so-called antibodies, against antigenic sites on the organisms or foreign material.
For reasons not yet completely understood, certain antigenic materials, known as allergens, often induce a hypersensitive response in human beings. This hypersensitivity, or allergy, can manifest itself in a number of readily identifiable symptoms, notably, hay fever, asthma, eczema, hives and localized swelling.
Traditionally, diagnostic analysis for the presence of this hypersensitivity in patients was accomplished with skin tests or provocation tests. In provocation tests the patient inhales the suspected allergen in aerosol form, whereas skin tests require applying the allergen to the patient's skin. Both tests necessitate monitoring the patient for evidence of allergic symptoms and require significant amounts of trained personnel time for proper evaluation. Moreover, in some cases exposure to the allergen can induce a strong allergic response, resulting in unnecessary discomfort, or even harm, to the patient.
As a result of discovery that a class of immunoglobulins, specifically IgE class antibodies, were in large part responsible for the allergic response, diagnosticians developed in vitro tests for IgE class antibodies utilizing standard radioimmunoassay techniques on serum. By way of example, several types of such tests can be found in U.S. Pat. Nos. 3,877,307 and 4,243,651.
Successful research was also accomplished with respect to techniques for the screening of different IgE class antibodies, and by way of example, such techniques can be found in U.S. Pat. Nos. 3,941,876 and 4,031,197. Basically, the techniques described in these patents include coating an elongated cellulosic body (e.g., a strip of paper) with separate identified allergens to form bands or islands, which are separated from one another by allergen-free areas. When this elongated body of cellulose material coated with the allergens is contacted with a test serum, serum IgE class antibodies specific for the coated allergens will attach to the appropriate places. After washing the cellulosic body and subsequently incubating it with labeled antibodies that are reactive with the attached IgE class antibodies, the bands and islands are analyzed for the presence of labeled antibodies. The information gleaned from the analysis provides an indication of the patient's allergic tendencies.
The methods and apparatus described in connection with the aforementioned screening patents are acceptable. However, the manufacture of the bands and islands on the cellulosic material is somewhat arduous and time consuming, typically requiring use of a jig for proper allergen coating. Also, for best results, all of the allergens should be coated on the cellulosic material at one time, mandating simultaneous allergen preparation. These constraints encumber the manufacturing process and limit the flexibility of the screening.
Accordingly, those concerned with the development and use of immunoassay techniques and related apparatus have recognized the desirability for further improvement in allergy screening systems. In particular, there has been a desire for improved and more economical manufacturing methods of devices useful for such screening. The present invention fulfills these needs.